1. Field of the Invention
The present invention relates to the field of underwater lighting systems and more particularly, to underwater lighting systems for the illumination of decorative water displays and the like.
2. Prior Art
Decorative water displays, or fountains as they are often called, of very elaborate designs and characteristics are often used for the aesthetic enhancement of buildings, shopping centers and the like. Such water displays may be substantially static, or with the advent of computer control, may provide constantly changing displays for even greater interest and aesthetic appeal. Typically such displays are lighted at night by high intensity lights disposed beneath the water level in a pool surrounding the water display, with the lights illuminating the display from the viewing sides so that the entire height of the water may be illuminated. Such lighting grossly enhances the appearance of the display, and in most cases is either the only form of lighting reasonably practical, or at least is the least intrusive.
Conventional underwater lighting systems have certain characteristics which are less than ideal, and which limit the visual effects which may be obtained thereby. One of these characteristics is the tendency of underwater lights to give off some light which ultimately proceeds from the light source, through the water surface and directly to the observer's eye rather than passing to the water display for illumination thereof. This creates an apparent glare just below the water display, having a substantial veiling effect on the illuminated water display itself.
The direct transmission of light to the eyes of the observer of the water display is caused by a number of factors characteristic of prior art lighting systems. The first, of course, is the lack of focus of the light source itself. Generally lights used underwater have a curved lens, with the result that the index of refraction of the water causes a spreading of the light rays upon entering the water, even if the light was reasonably well focused within the light source itself. While underwater lighting units having a flat lens at the lens-water interface are known, such as shown in U.S. Pat. No. 1,968,072, such flat lenses are frequently used, as in that patent, in swimming pools wherein dispersed lighting rather than focused lighting is desired.
U.S. Pat. No. 2,481,054 discloses a light projector which is configured to minimize light passing substantially along a line of sight between the light projector and a water display observer by blocking that light from the sides and using a concave lens over the light. That system does not address another major cause of light passing directly to the observer's eyes, specifically the effect of ripples on the top of the pool of water caused by and constantly present due to the water display itself. Consequently, even the best focussed underwater light unit will still result in substantially dispersed light upon passing through the real water-air interface at the surface of the pool, again causing some veiling effect.
The light dispersion at the surface of the pool has another undesirable effect. In particular, lighting a water display with a colored light causes the water display to appear to itself be comprised of glowing colored water. Ideally in some instances one would like to illuminate different parts of the display with different colors to further enhance the appearance thereof. However, when one attempts this with prior art lighting systems, the dispersion of the light caused by the water surface, either alone or in conjunction with other factors, results in the intermixing of the various colors, which of course results in white light, contrary to the desired result.